what does nitrous oxide do? 
Laughing gas.
She asked what does it do. It does not make you laugh.
I makes you hallucinate. If you inhale it on its own you will hear an echo effect and feel a bit spacey.
The fun comes with inhaling when you are on another substance - eg. pot or lsd - you will go on a magical journey, forget who you are, forget you even took the drug, see impossible things and come back (closer) to reality within a minute or two. Good fun.
